The present invention relates generally to laser (or other high intensity light) markable media used, for example, as labels in labeling machines and/or in film printing for, packaging, or for other printing applications, including point-of-sale, fax machines and laminate card (e.g. identity card) printers.
The labeling and packaging markets are demanding marking systems that are faster, more cost effective, capable of marking non-flat surfaces that have a longer lifetime, and which are capable of marking labels or packaging films “on the fly.”
As known in the prior art, direct laser array marking of high volume label media has a number of advantages: no ink or ribbon, non-contact (giving longer head lifetime), and allowing non-flat media or printing on non-flat substrates; see published PCT patent application WO 05/049332—published Feb. 06, 2005.
As is also known in the prior art, diode laser arrays provide a low cost, compact, high-speed, high reliability solution for marking rolls of labels to be applied to produce.
A major disadvantage of prior art direct laser marking systems is that they require media sensitive to NIR (near infrared) wavelength of diode lasers. The traditional approach requires an NIR (near infrared) absorber with a narrow absorption band, because any residual absorption in the visible wavelength range will cause visible coloration of the media. In most cases, white or clear media is preferred, so coloration is undesirable. Additionally, narrowband NIR absorbers can be costly, adding significantly to the cost of the media, when used in applications like packaging/product labeling, where costs need to be extremely low.
The present invention overcomes the aforementioned problems with the prior art systems.
The present invention includes a way to create laser markable media for NIR lasers, while avoiding the need for narrowband NIR absorbers.
More particularly, one embodiment of the invention includes a novel “indirect” light markable, multi-layer media wherein laser output light (or other high intensity light) is absorbed and converted into heat by one layer of the media, is immediately thermally conducted into selected portions of an adjacent, thermochromic layer, and forms the desired image. The “indirect” markable media preferably utilizes a three layer label laminate (in addition to any adhesive layer), including a layer of light absorbent material (preferably carbon black) which overlies or is embedded in the front surface of a translucent plastic substrate. The media can be “back marked” or “front marked.” In the case of “back marking,” in one embodiment the preferred carbon black absorbs the output light energy of the laser (or other high intensity light) output beam or beams, after the beam or beams have passed through the translucent label substrate, and converts the absorbed light energy into heat; the heat is conducted into a thermochromic front or visible layer, causing desired portions of the thermochromic layer to change color (or visual appearance) to produce the desired image.
In a “front marking” mode, in one embodiment the light output beam passes through the “front” of the media, that is the thermochromic layer first, then enters the light absorbent layer.
The present invention includes further features for optimizing the overall efficiency of the system, including the use of reflective materials either in the thermochromic coating or on the front surface of the thermochromic coating, and in the use of obscuration techniques, to obscure the carbon black (or other) light absorbent layer, described in detail below.
The laser markable label prior art includes (in addition to WO 05/049332 noted above) the use of carbon black as an ablatable layer and as a donor [see U.S. Pat. No. 6,001,530 (see col. 4, lines 53-58); U.S. Pat. No. 6,140,008 (see col. 2, lines 57-59); U.S. Pat. No. 6,207,344 (see col. 2, lines 47-50); US 2005/0115920 A1 (see page 2, paragraph [0016]) and U.S. Pat. No. 7,021,549 (see col. 3, lines 39-43)]. However, that prior art does not teach or suggest the use of carbon black as a light absorbent material wherein the absorbed light is converted to heat and conducted into an adjacent thermochromic layer; neither does it teach or suggest a three layer label laminate having a light absorbent central layer, a thermochromic layer and a substrate.
The present invention is applicable to the automatic labeling of fruit and vegetables. More particularly, the invention provides an improved laminated label structure for use in a system for applying variable information “on the fly” to labels for single items of produce. The invention greatly reduces the number of labeling machines, label designs, and label inventory needed to automatically apply labels to produce. The invention simplifies packing operations and reduces costs by reducing the labor and label inventory required to automatically label produce.
A primary object of the invention is to provide a laser (or other high intensity light source) markable, multi-layer media for use as labels or in film printing incorporating a low cost light absorbent layer for NIR lasers, while avoiding the need for expensive narrowband NIR absorbers and removing residual media coloration.
A further object of the invention is to provide an “indirect” laser (or other high intensity light source) markable, multi-layer media which can be marked either through the front or back surface of the media.
A further object of the invention is to provide a laser markable, multi-layer media in which a low cost, broadband light absorbent layer, such as carbon black, for example, absorbs laser light output and converts absorbed light into heat, and the absorbed heat is conducted into portions of an adjacent thermochromic layer to form the desired image.
Another object of the invention is to provide a laser (or other high intensity light source) markable, multi-layer media including a light absorbent layer as noted above together with obscuration means to prevent said light absorbent layer from being visible to the naked eye.
A further object of the present invention is to provide a multi-layered media for use in automatic labeling machines for applying labels to single items of produce wherein variable coded information is applied to each label immediately prior to its application to an item of produce.
A further object of the invention is to provide a laminated label design capable of having variable coded information applied to it after the label has been transferred to the tip of a bellows in a rotary bellows applicator, which requires only minor modifications to the rotary bellows label applicating machine.
A further object of the invention is to provide a laminated label capable of having variable coded information applied to it for use in a rotary bellows applicator without having to reduce the operating speed of the rotary bellows applicator.
Further objects and advantages will become apparent from the following description and drawings wherein: